Ada 编程/库/Ada.Containers.双向链表

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此语言功能仅从 Ada 2005 开始提供。

Ada.Containers.Doubly_Linked_Lists 是自 Ada 2005 以来 预定义语言环境 的一个单元。

简介

Ada 2005 的主要新增功能之一是 容器 库。此库使 Ada 开发人员能够操纵数据结构，如双向链表、映射、集合和向量。本页面将展示 Ada.Containers.Doubly_Linked_Lists 库的工作原理。

双向链表只是一种链表，其中每个元素不仅链接到下一个元素，还链接到上一个元素。有关更多信息，请参见 双向链表。

示例

这是来自现有项目的示例用法。

worm.ads

此文件表示蠕虫的规范。

with Ada.Containers.Doubly_Linked_Lists;
with Wormlevel, Protocol; -- , Handlers;
 
package Worm is
  
  use Wormlevel, Protocol; -- , Handlers;
  
  package Worm_Position_Container is new Ada.Containers.Doubly_Linked_Lists(Position);
  use Worm_Position_Container;
  
  type Worm_State is (Alive,Dead,Observing);
 
  type Worm_Type is
     record
        Worm_Body : List;
        Direction : Course  := North;
        Points    : Natural := 0;
        Number    : Positive;
        State     : Worm_State := Alive;
        Full      : Boolean := False;
     end record;
  type Worm_Type_Access is access Worm_Type;
  procedure Update_Worm (Worm : in Worm_Type_Access;
                         Lvl  : in Level_Access);
  procedure Turn_Left   (Worm : in Worm_Type_Access);
  procedure Turn_Right  (Worm : in Worm_Type_Access);
  procedure Kill        (Worm : in Worm_Type_Access);
 
end Worm;

如您所见，Ada.Containers.Doubly_Linked_Lists 使用名为“Position”的类型实例化。此类型表示二维数组中的瓦片类型。蠕虫主体现在由双向链表表示，这意味着我们可以使用 Next 和 Previous 函数，在任一方向遍历每个元素。

对于有兴趣的人来说，该游戏可以在 GitHub 上找到。

规范

--                     Standard Ada library specification
--   Copyright (c) 2003-2018 Maxim Reznik <reznikmm@gmail.com>
--   Copyright (c) 2004-2016 AXE Consultants
--   Copyright (c) 2004, 2005, 2006 Ada-Europe
--   Copyright (c) 2000 The MITRE Corporation, Inc.
--   Copyright (c) 1992, 1993, 1994, 1995 Intermetrics, Inc.
--   SPDX-License-Identifier: BSD-3-Clause and LicenseRef-AdaReferenceManual
-- -------------------------------------------------------------------------

generic
   type Element_Type is private;

   with function "=" (Left  : in Element_Type;
                      Right : in Element_Type)
                     return Boolean is <>;

package Ada.Containers.Doubly_Linked_Lists is

   pragma Preelaborate (Doubly_Linked_Lists);

   type List is tagged private;
   pragma Preelaborable_Initialization (List);

   type Cursor is private;
   pragma Preelaborable_Initialization (Cursor);

   Empty_List : constant List;

   No_Element : constant Cursor;

   function "=" (Left  : in List;
                 Right : in List)
                return Boolean;

   function Length (Container : in List) return Count_Type;

   function Is_Empty (Container : in List) return Boolean;

   procedure Clear (Container : in out List);

   function Element (Position : in Cursor) return Element_Type;

   procedure Replace_Element (Container : in out List;
                              Position  : in     Cursor;
                              New_Item  : in     Element_Type);

   procedure Query_Element
     (Position : in Cursor;
      Process  : not null access procedure (Element : in Element_Type));

   procedure Update_Element
     (Container : in out List;
      Position  : in     Cursor;
      Process   : not null access procedure (Element : in out Element_Type));

   procedure Move (Target : in out List;
                   Source : in out List);

   procedure Insert (Container : in out List;
                     Before    : in     Cursor;
                     New_Item  : in     Element_Type;
                     Count     : in     Count_Type := 1);

   procedure Insert (Container : in out List;
                     Before    : in     Cursor;
                     New_Item  : in     Element_Type;
                     Position  :    out Cursor;
                     Count     : in     Count_Type := 1);

   procedure Insert (Container : in out List;
                     Before    : in     Cursor;
                     Position  :    out Cursor;
                     Count     : in     Count_Type := 1);

   procedure Prepend (Container : in out List;
                      New_Item  : in     Element_Type;
                      Count     : in     Count_Type := 1);

   procedure Append (Container : in out List;
                     New_Item  : in     Element_Type;
                     Count     : in     Count_Type := 1);

   procedure Delete (Container : in out List;
                     Position  : in out Cursor;
                     Count     : in     Count_Type := 1);

   procedure Delete_First (Container : in out List;
                           Count     : in     Count_Type := 1);

   procedure Delete_Last (Container : in out List;
                          Count     : in     Count_Type := 1);

   procedure Reverse_Elements (Container : in out List);

   procedure Swap (Container : in out List;
                   I         : in     Cursor;
                   J         : in     Cursor);

   procedure Swap_Links (Container : in out List;
                         I         : in     Cursor;
                         J         : in     Cursor);

   procedure Splice (Target : in out List;
                     Before : in     Cursor;
                     Source : in out List);

   procedure Splice (Target   : in out List;
                     Before   : in     Cursor;
                     Source   : in out List;
                     Position : in out Cursor);

   procedure Splice (Container : in out List;
                     Before    : in     Cursor;
                     Position  : in     Cursor);

   function First (Container : in List) return Cursor;

   function First_Element (Container : in List) return Element_Type;

   function Last (Container : in List) return Cursor;

   function Last_Element (Container : in List) return Element_Type;

   function Next (Position : in Cursor) return Cursor;

   function Previous (Position : in Cursor) return Cursor;

   procedure Next (Position : in out Cursor);

   procedure Previous (Position : in out Cursor);

   function Find (Container : in List;
                  Item      : in Element_Type;
                  Position  : in Cursor := No_Element)
                 return Cursor;

   function Reverse_Find (Container : in List;
                          Item      : in Element_Type;
                          Position  : in Cursor := No_Element)
                         return Cursor;

   function Contains (Container : in List;
                      Item      : in Element_Type)
                     return Boolean;

   function Has_Element (Position : in Cursor) return Boolean;

   procedure Iterate
     (Container : in List;
      Process   : not null access procedure (Position : in Cursor));

   procedure Reverse_Iterate
     (Container : in List;
      Process   : not null access procedure (Position : in Cursor));

   generic
      with function "<" (Left  : in Element_Type;
                         Right : in Element_Type)
                        return Boolean is <>;

   package Generic_Sorting is

      function Is_Sorted (Container : in List) return Boolean;

      procedure Sort (Container : in out List);

      procedure Merge (Target : in out List;
                       Source : in out List);

   end Generic_Sorting;

private

   type List is tagged null record;

   Empty_List : constant List := (null record);

   type Cursor is null record;

   No_Element : constant Cursor := (null record);

end Ada.Containers.Doubly_Linked_Lists;

参见

华夏公益教科书

• Ada 编程/库/Ada

外部示例

• 在以下位置搜索 Ada.Containers.Doubly_Linked_Lists 的 示例： Rosetta Code、GitHub (gists)、任何 Alire 包 或 本华夏公益教科书。
• 在以下位置搜索与 Ada.Containers.Doubly_Linked_Lists 相关的 帖子： Stack Overflow、comp.lang.ada 或 任何与 Ada 相关的页面。

Ada 参考手册

Ada 2005

• A.18.3: 包 Containers.Doubly_Linked_Lists ^[注释]

Ada 2012

• A.18.3: 泛型包 Containers.Doubly_Linked_Lists ^[注释]

开源实现

FSF GNAT

• 规范： a-cdlili.ads
• 主体： a-cdlili.adb

drake

• 规范： containers/a-cdlili.ads
• 主体： containers/a-cdlili.adb